Study On The Interaction Of Some Active Components In Chinese Traditional Medicines With Human Serum Albumin

Human serum albumin (HSA), the major soluble protein constituents of thecirculatory system, is the most important drug carrier protein with a highconcentration in blood plasma and has many physiological functions. It can bindmany exogenous and endogenous ligands in blood, and realize transport anddistribution of many molecules and metabolites. Protein-drug interaction has a greatinfluence upon the distribution of the drugs in the body, upon their patterns ofmetabolism and excretion. Investigating the binding mechanism of drugs binding toHSA can provide an importance theoretical base on discussing human diseasemechanism, diagnosis and prevention of diseases, pharmaceutical industry anddevelopment new drugs. Thus, it has been an interesting research field of toxicology,life sciences, chemistry, pharmacokinetics, and clinical medicine. On the basis of theprevious research, the following major innovative works were carried out in thisdissertation:(1) Several methods were associated to study the interaction of four components of Chinese herb medicine (puerarin, honokiol, tanshinoneⅡA and methyl hesperidin) and methyl hesperidin.(2) The binding properties including the fluorescence quenching mechanisms, binding constants and the number of binding sites were investigated in detail, thermodynamic parameters were calculated, and the main interaction force between drugs and proteins was discussed.(3) The computational modeling method was used to study the drug-HSA interaction and the study results were in consistent with the experimental results.(4) The effects of drugs on HSA second structure were investigated with FT-IR and circular dichroism techniques.This dissertation consists of seven chapters:Chapter 1:The structures, functions and natures of proteins were briefly introducedThe contents,methods and evolvement of interaction of different kind of smallligands with protein were reviewed in detail. Chapter 2: The binding of puerarin to HSA has been investigated for the first timeby the fluorescence method, FT-TR, CD spectroscopy and molecular modeling. Theresult has clearly indicated that puerarin is a strong quencher and can bind tightly toHSA with changing slightly its molecular conformation. Meanwhile, from the resultsof binding mode and molecular modeling, it can be revealed that puerarin has boundwithin the subdomainⅡA of HSA mainly by the hydrophobic interaction andhydrogen bond.Chapter 3: The interaction between honokiol and HSA has been investigated bydifferent optical techniques and molecular modeling method. The data of fluorescenceanisotropy indicated that the binding of honokiol changed the microenvironment ofHSA. In addition, the results of CD and FT-IR spectroscopy showed that thesecondary structure of HSA was changed after honokiol bound to HSA. Furthermore,according to the molecular modeling study, honokiol can strongly bind to the site I(subdomainⅡA) of HSA mainly by hydrophobic force and there was also hydrogenbond interaction between honokiol and the residue Arg-222.Chapter 4: The binding of tanshinoneⅡA with HSA have been studied using UVabsorption spectroscopy, fluorescence spectroscopy, FT-IR spectra and molecularmodelling methods under simulative physiological conditions respectively. Thebinding constants, numbers of binding site, mainly intermolecular force and thechanges of HSA secondary structure induced by drugs binding were obtained. Inaddition, the results of binding mode and molecular modeling study showed thattanshinoneⅡA can strongly bind to the site I (subdomainⅡA) of HSA mainly byhydrophobic force and there was also hydrogen bond interaction between them.Chapter 5: The interaction between methyl hesperidin (MH) and HSA has beeninvestigated in vitro under simulated physiological conditions using different opticaltechniques. The results have clearly indicated that MH is a strong quencher and canbind tightly to HSA with changing its molecular conformation. Meanwhile, from theresults of binding mode, it can be revealed that the acting forces are mainly thehydrophobic interaction. According to the F(o|¨)rster theory of molecular resonanceenergy transfer, the distance r between the protein residue (donor) to MH (acceptor) in HSA is smaller than 7 nm suggesting that the energy transfer between HSA and MHcan occur with high possibility.Chapter 6: The binding properties (including binding mechanism, binding constant,and the number of binding sites) of thiophanate methyl (MT) to HSA at threetemperatures under simulative physiological conditions have been studied utilizingfluorescence method. Meanwhile, the effect of MT on the structure of HSA wasstudied using UV and Fourier transform infrared (FT-IR).Chapter 7: The nearly monodisperse starch capped CdSe nanoparticles weresuccessfully synthesized by a simple and "green" route at room temperature. It is amild, simple, cheap and efficient "green" route for producing nanoparticles. Theas-prepared nanoparticles were characterized by X-ray diffraction (XRD),Transmission Electron Microscope (TEM), UV-vis absorption andPhotoluminescence (PL) spectra. The results indicated stable and well dispersed CdSenanoparticles with fairly narrow size distributions were synthesized.